Hi Quentin, > On 1/21/25 10:41 AM, Quentin Schulz <quentin.schulz@xxxxxxxxx> wrote: > > Hi Lukasz, > > On 1/21/25 10:22 AM, Lukasz Czechowski wrote: > > UART controllers without flow control seem to behave unstable > > in case DMA is enabled. The issues were indicated in the message: > > https://lore.kernel.org/linux-arm-kernel/CAMdYzYpXtMocCtCpZLU_xuWmOp2Ja_v0Aj0e6YFNRA-yV7u14g@xxxxxxxxxxxxxx/ > > In case of PX30-uQ7 Ringneck SoM, it was noticed that after couple > > of hours of UART communication, the CPU stall was occurring, > > leading to the system becoming unresponsive. > > After disabling the DMA, extensive UART communication tests for > > up to two weeks were performed, and no issues were further > > observed. > > The flow control pins for uart5 are not available on PX30-uQ7 > > Ringneck, as configured by pinctrl-0, so the DMA nodes were > > removed on SoM dtsi. > > > > Reviewed-by: Quentin Schulz <quentin.schulz@xxxxxxxxx> > > We should backport this to stable releases too, so please follow the > instructions from here: > https://www.kernel.org/doc/html/latest/process/submitting-patches.html#select-the-recipients-for-your-patch > > Essentially: > > Cc: stable@xxxxxxxxxxxxxxx > > in the commit log and we'll need a > > Fixes: <commit hash> > > trailer as well with the commit hash of the commit introducing the issue > (likely the one defining uart5 for Ringneck for us). > > Considering that UART0 CTS and RTS are routed to Q7 header but only > usable when Haikou exposes UART0 on the DB9 connector (via the SW2 > switch), which is NOT the default state (and in any case not supported > by our current device tree), I believe we should make the same change to > the uart0 node in haikou dts for Ringneck. What do you think? Can you > send another patch for that one? It seems that in case of uart0, that is configured as kernel console, the DMA is not used by the kernel: https://lore.kernel.org/linux-serial/20200217114016.49856-7-andriy.shevchenko@xxxxxxxxxxxxxxx/ Which is likely why the issue was not observed so far. However it might be good to do the same change to be on the safe side. Should I extend this patch series with the fix for the Haikou device tree then, or create a new one? > > Thanks! > Quentin Best Regards, Lukasz
